feat(native): Tier B — WinRT rich toasts (P5-41/35) + Focus Assist sync (P5-56)

- toast.rs: Windows.UI.Notifications rich toast (reply input + Send action);
  in-process Activated event → emit lotus-notification-activate {path} (click) /
  lotus-notification-reply {roomId,text}. Falls back to tauri-plugin-notification
  (WinRT error / non-Windows). The NOTIFICATION_BRIDGE now routes notifications
  carrying a roomId (tag) to show_rich_toast. Features: UI_Notifications,
  Data_Xml_Dom, Foundation_Collections.
- focus_assist.rs: SHQueryUserNotificationState poll thread → emit
  focus-assist-changed {active} on QUNS_QUIET_TIME/PRESENTATION/D3D_FULLSCREEN/BUSY.
  No new Cargo features.

CI Windows compile pending (no local Rust toolchain). Runtime caveat: WinRT toasts
need a Start-menu shortcut + matching AppUserModelID (org.lotusguild.lotus-chat);
without it CreateToastNotifier errors and the code falls back to the plugin.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -51,10 +51,21 @@ const NOTIFICATION_BRIDGE: &str = r#"(function(){
   function TauriNotification(title,options){
     var opts=options||{};
     try{
-      window.__TAURI_INTERNALS__.invoke('send_notification',{
-        title:String(title),
-        body:opts.body!=null?String(opts.body):undefined
-      }).catch(function(){});
+      var body=opts.body!=null?String(opts.body):undefined;
+      // cinny tags message notifications with the roomId (options.tag) and the
+      // in-app route (options.data.path). When present, route to the rich WinRT
+      // toast (click-opens-room + quick reply); otherwise a plain toast.
+      var roomId=opts.tag!=null?String(opts.tag):undefined;
+      var path=(opts.data&&opts.data.path!=null)?String(opts.data.path):undefined;
+      if(roomId){
+        window.__TAURI_INTERNALS__.invoke('show_rich_toast',{
+          title:String(title),body:body,roomId:roomId,path:path
+        }).catch(function(){});
+      }else{
+        window.__TAURI_INTERNALS__.invoke('send_notification',{
+          title:String(title),body:body
+        }).catch(function(){});
+      }
     }catch(_){}
   }
   TauriNotification.prototype=Object.create(EventTarget.prototype);
@@ -397,6 +408,7 @@ pub fn run() {
             native::chrome::window_toggle_maximize,
             native::chrome::window_start_drag,
             native::chrome::window_close,
+            native::toast::show_rich_toast,
         ])
         .plugin(tauri_plugin_localhost::Builder::new(port).build())
         .plugin(tauri_plugin_window_state::Builder::default().build())